%0 Journal Article
%T CsmA Protein is Associated with BChl a in the Baseplate Subantenna of Chlorosomes of the Photosynthetic Green Filamentous Bacterium Oscillochloris trichoides belonging to the Family Oscillochloridaceae
%A Anastasiya Zobova
%A Alexandra Taisova
%A Eugeny Lukashev
%A Nataliya Fedorova
%A Ludmila Baratova
%A Zoya Fetisova
%J Journal of Biophysics
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/860382
%X The baseplate subantenna in chlorosomes of green anoxygenic photosynthetic bacteria, belonging to the families Chloroflexaceae and Chlorobiaceae, is known to represent a complex of bacteriochlorophyll (BChl) a with the ~6 kDa CsmA proteins. Earlier, we showed the existence of a similar BChl a subantenna in chlorosomes of the photosynthetic green bacterium Oscillochloris trichoides, member of Oscillochloridaceae, the third family of green photosynthetic bacteria. However, this BChl a subantenna was not visually identified in absorption spectra of isolated Osc. trichoides chlorosomes in contrast to those of Chloroflexaceae and Chlorobiaceae. In this work, using room and low-temperature absorbance and fluorescence spectroscopy and sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of alkaline-treated and untreated chlorosomes of Osc. trichoides, we showed that the baseplate BChl a subantenna does exist in Oscillochloridaceae chlorosomes as a complex of BChl a with the 5.7 kDa CsmA protein. The present results support the idea that the baseplate subantenna, representing a complex of BChl a with a ~6 kDa CsmA protein, is a universal interface between the BChl c subantenna of chlorosomes and the nearest light-harvesting BChl a subantenna in all three known families of green anoxygenic photosynthetic bacteria. 1. Introduction Green anoxygenic bacteria comprise three phylogenetically unrelated families of photosynthetic bacteria: green sulfur bacteria (family Chlorobiaceae) and green filamentous bacteria (families Chloroflexaceae and Oscillochloridaceae) [1¨C3]. In 2000, the genus Oscillochloris was excluded from the family Chloroflexaceae, and a new family Oscillochloridaceae was proposed based on phylogenetic data and unique physiological, biochemical, and chemotaxonomical properties [3]. The photosynthetic apparatus of green anoxygenic bacteria has a particular molecular organization and contains chlorosomes, unique extramembrane light-harvesting antennae structures [4, 5]. The group of chlorosome-containing bacteria was enlarged by the recently discovered new phototrophic chlorosome-containing organism Candidatus Chloracidobacterium thermophilum from the phylum Acidobacteria [6], and it is a surprising fact. Chlorosomes are ellipsoid oblong bodies of about 70¨C260£¿nm long, 30¨C100£¿nm wide, and 10¨C30£¿nm thick (depending on the species) attached to the inner surface of the cytoplasmic membrane. They are enveloped by a protein-lipid monolayer of 2-3£¿nm width [7]. The bulk of light-harvesting pigments (including various types of
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